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By Shadia J. Ikhmayies

"Tin oxide (SnU2) thin films of thicknesses in the range 100-600 nm were prepared on glass substrates by vacuum evaporation at ambient temperature. The films were characterized by transmittance measurements, X-ray diffraction (XRD), scanning electron microscope (SEM) observations and energy dispersion X-ray analysis (EDAX). It is found that the films have high transmittance and non sharp absorption edges. XRD diffractograms showed that the films are amorphous and the SEM micrographs showed that the surfaces are smooth, uniform and well covered with the material. The EDAX analysis showed that the films are deficient in oxygen. Indirect optical bandgap energy and Urbach tailing in the bandgap was observed, and the width of the tail, which is related with disorder and localized states, was estimated.IntroductionTin oxide is an n-type wide bandgap semiconducting material with a direct bandgap energy of 4 eV and an indirect bandgap of 2.6 eV [1], where inherent oxygen vacancies act as an n-type dopant [2], Tin oxide thin films have been used for transparent electrodes in photoelectric conversion devices namely amorphous silicon solar cells, liquid crystal displays, gas discharge displays, etc. [3]. Perfectly amorphous thin SnO2 films show good electrical response to reducing gases in air and could, hence, be applied to construct semiconductor gas sensors where the metal oxide films function as a monograin-eqivalent active layer [4]. Amorphous SnU2 can also be used in extended gate field-effect transistors (EGFET) as a pH sensor, where the sensitive part is made of the SnO2/Al structure. This device can be used to detect and to quantify any kind of substance that can produce or consume protons, like an enzymatic reaction, therefore showing a large range of applications as biosensors [5].There are different methods to prepare SnO2 films, such as atomic layer deposition (ALD) [6], reactive magnetron sputtering [7], chemical vapor deposition [8, 9], dip coating [10], spray pyrolysis (SP) [3, 11-14], and evaporation [8], The thermal evaporation method was chosen to produce SnO2 thin films in this work because deposition by this technique does not present any compositional problems. In addition, it is a low temperature technique, which increases the probability of producing amorphous films. To increase this probability, the films were deposited at ambient temperature."

Jan 1, 2012

By Jose Carlos D'Abreu, Edelink Efrain Tinoco Falero, Mauricio Marcos Otaviano

The production and consumption of Direct Reduced Iron (DRI) are continuously increasing, as a consequence of the impact of shale gas extraction technology on the Natural Gas (NG) market. Considering this context, DRI may improve the Blast Furnace (BF), Electric arc Furnace (EAF) and LD converter ’s productivities and consequently their competitiveness. In this work the results of a cooperative research conducted by PUC-Rio University and a Brazilian mining company are presented. Laboratory-scale simulation tests, using DR commercial pellets and typical industrial operational parameters of a benchmarked DR shaft furnace, were conducted and planned using statistical and factorial analysis. In the simulated experiments, the following three regions of the DR shaft furnace were considered: Reduction Zone (RZ), Transition Zone (TZ) and Cooling Zone (CZ). Three stages were considered in the research development: (i) the reactions and equations concerning pellet metallization and Carbon precipitation were analyzed; (ii) experiments focused on the de finition of the carburization kinetic equations occurring in the Transition and Cooling zones, and finally, (iii) aimed to develop the “METCARB” model, a computational program conceived to simulate mathe- matically the metallization and carbonization reactions along the height of the furnace. In conclusion, a comparison is made with industrial results in order to validate the resulting “METCARB” model.

Mar 1, 2018

By Zbigniew Zurecki

The selection of atmosphere composition is critical for controlling surface quality of reactive aluminum alloys during solution treatments. An improper selection of annealing atmosphere can result in surface blistering in AI-Mg and sub-surface depletion of lithium in AI-U ingots. To determine optimum atmosphere compositions for homogenizing A1-Mg and Al-Li alloys, Ii number of exploratory experiments were carried out in air, nitrogen, and carbon dioxide based atmospheres including reactive impurities or additive such as moisture and sulfur hexafluoride. This paper describes the influence of these atmospheres on high-temperature oxidation and sub-surface defects. The results are discussed in terms of the change in Pilling-Bedworth ratio.

Jan 1, 1996

By Denise Nascimento, Alice Barreto Bevitori, Felipe Perissé Duarte Lopes, Renan Carreiro, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"Natural fibers obtained from plants have increasingly been used as reinforcement of polymeric composites in engineering applications. This is the case of the fiber extracted from the piassava palm tree, a native of the southeast region of South America, which for a long time has been used in simple items like brooms and brushes. Recently it was reported that the tensile strength of the piassava fiber varied inversely with the equivalent diameter. Following that previous work, the elastic modulus and the density dependence on the diameter of stiffer piassava fibers of the Attalea fiinifera species was investigated. Precise measurements with a profile projector and Weibull analysis of the experimental results indicated that both the elastic modulus and the density of piassava fibers also follow an inverse correlation with the diameter. Scanning electron microscopy observations of the microstructure and fracture surface showed that defects and participation of microfibrils are responsible for this correlation.IntroductionIn the past decades, both the increase in the price of the petroleum and climate changes due to greenhouse gas emissions are motivating the use of renewable and low cost natural materials as a substitute for energy intensive and CO2 contributor synthetic materials [1]. A typical case is that of natural cellulose-based fibers extracted from cultivated plants in comparison to glass fibers, which are extensively used for composite reinforcement. In fact, these natural lignocellulosic fibers are increasingly being investigated [2-6] as possible reinforcements of polymeric composites, and in some cases, successfully replacing glass fiber composites in engineering applications [7]. The automobile industry has remarkable examples of lignocellulosic fiber composite substitutions [8-10]. Not only do some of these fibers display specific mechanical properties comparable to glass fibers but their composites also contribute to lower equipment wear and better finishing of molded components [6]."

Jan 1, 2012

By C. Hennesmann, D. Maijer, S. L. Cockcroft, P. Yo

"Die cast aluminum wheels are one of the most difficult automotive castings to produce because of stringent cast surface and internal quality requirements. As part of a collaborative research agreement between researchers at the University of British Columbia and Canadian Auto Parts Toyota Incorporated, work has been underway to predict heat transport and porosity formation in die cast A356 wheels. The basic heat transfer equations have been solved using the commercial finite element package ABAQUS to which specialized routines have been added to predict porosity. Preliminary work on predicting porosity formation focused on using the Niyama parameter as a measure of the probability of porosity. The latest version of the model incorporates a new fundamentally based porosity criterion, which takes into account the effect of hydrogen concentration. The development of this model together with its application to a series of cylindrical test castings as well as a production cast wheel are presented.I. IntroductionDie cast aluminum wheels are one of the most difficult automotive castings to produce because of stringent cast surface and internal quality requirements. Microporosity, in particular, is a common defect that can adversely affect wheel quality. The mechanism of microporosity formation in aluminum alloys is complex owing to its dependence on the interaction of a number of phenomena occurring during solidification including the decrease in hydrogen solubility, the decrease in volume, the development of the solidification structure, and the increase in difficulty in interdendritic feeding [1]. As a result, the amount, size, and distribution of microporosity is affected by a large number of casting parameters including thermal variables, melt composition, grain structure, modification, and inclusion content, making optimization by trial-and-error methodologies difficult.The use of criteria functions, based on thermal conditions during casting, offers a relatively simple approach to predicting microporosity. In practical terms, they are useful because they provide a straightforward method of assessing the impact of varying casting parameters on porosity through various thermal parametersl21 such as thermal gradient, cooling rate, solidification time, and solidus velocity. Drawbacks of criteria functions include insensitivity to varying hydrogen concentration and the limitation to qualitative predictions. Consequently, in aluminum alloys, attempts have been made to develop models incorporating the effects of hydrogen gas and microstructure evolution. However, these types of models represent a significant increase in complexity and sacrifice the simplicity and ease of application of the thermally based criteria functions."

Jan 1, 2001

By Antonio de Lucas, Juan Francisco Rodríguez, Ignacio Gracia, Mª Teresa García

"The amount of waste of Polystyrene (PS) foams is increasing in last years due to their use in insulation, protecting and, storing many different food products. Conventional methods of recycling such as crushing and shrinking by heated air or frictional heat have the disadvantages of molecular degradation, resulting in a reduction of the quality of the recycled polymer. Dissolution and shrinking with suitable solvents is one of the cheapest and more efficient ways of polystyrene recycling but in the process of the solvent recovery by distillation a certain degree of molecular degradation is produced. In this way, CO2 supercritical technology appears as an interesting alternative for the elimination of solvent. This work proposes a global process to polystyrene recycling in two steps: a polystyrene dissolution with a suitable “green” solvent followed by its elimination by supercritical tecnologhy. In order to develop a “green process” the constituents of essential oils, limonene, terpinene, cymene, and phellandrene, are selected as the most appropriated solvents. Introduction In the last years, disposal of the non-biodegradable plastic wastes has been recognized as a serious environmental problem. Recycling these wastes has great interest in order to prevent the environmental pollution and to preserve natural sources (1, 2, 3). Since the Polystyrene foams (PS) is one of the most used foam in isolation, protecting and food storage most of recycling work is concerned with this polyolefin (4). The two main alternatives for treating polymer wastes are energy recycling, where wastes are incinerated, and mechanical recycling (5). Environmental argumentations such as toxic emissions are building up a public resistance against incineration process (6). Mechanical recycling is a popular recovery path for manufacturers and is carried out on single-polymer waste streams. Any way, the market for recycled products can only be found if the quality is close to that of the original. Unfortunately the process of classification and further recovery of these wastes makes them often more expensive than virgin plastic (7, 8). Solvent extraction is one of the cheapest and more efficient ways for PS recycling. If it is done in house of waste producers the separation between plastics could be easy and effective and the transport costs would be eliminated."

Jan 1, 2008

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process. The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By A. Dutta, B. Devulapalli, A. Mukhopadhyay, E. W. Grald

"Computational Fluid Dynamics (CFO) has matured over the past two decades as an analysis tool for conducting virtual experiments with significant time and cost savings. It complements and reduces physical testing. CFO has penetrated the diverse materials industry in much the same way as Computer Aided Design (CAD) did more than a decade ago. As the basic numerical algorithms used in CFO have steadily improved, so have the reliability, consistency and user-friendliness improved significantly, too. Other recent trends have also contributed to the rapid growth and widespread adoption of CFO. In this presentation, CFO applications from several materials processing industries will be presented using case studies. Emphasis will be on metals, glass and semiconductor applications.IntroductionThe term materials processing covers a diverse array of industrial applications and products today. From the continuous casting of steel, to the deposition of semiconductor materials atom by atom, to the extrusion of molten polymers, materials processing applications span an incredible range of length scale, process times, pressures, temperatures and velocities. The properties of the materials themselves, in terms of density, viscosity, thermal conductivity, etc., can be complex functions of temperature, shear rate, chemical composition and time. And the processing equipment may be very complicated in geometric shape.Computational fluid dynamics (CFD), the technique of solving the governing equations of fluid motion and other related phenomena using a computer, has enjoyed widespread and rapid growth, which started in the aerospace and automotive industries. More recently, CFD has also been successfully applied to a great many materials processing problems, in spite of the challenges described in the previous paragraph. The reasons for the growing usage of CFD in materials processing are many. Using CFD to test design options and reduce the number of physical prototypes can decrease the time and cost associated with new product and process development. CFD gives insight and provides detailed predictions of operating conditions in lieu of difficult, intrusive and often expensive experimental methods. CFD can be used as an aid to scale-up processes from lab or pilot scale to full production. Troubleshooting the performance of existing equipment is often carried out with the help of CFD. Determining how an existing piece of process equipment will operate under new conditions, or with new input ,materials, is also a common task for CFD."

Jan 1, 2004

By J. Bostjancic

As wastewater discharge regulations become more stringent, power plants, manufacturing plants and other industrial sites are looking for ways to reduce makeup water requirements and to recycle and reuse as much wastewater as possible. In some cases, environmental regulations require zero liquid discharge, meaning all wastewater must either be retained on site or reduced to solids for disposal off site. Zero liquid discharge or "closed-loop" wastewater treatment systems using evaporators and other process equipment have been well-accepted in recent years. Often overlooked is the fact that zero discharge is not just the latest fashion--many commercial zero liquid discharge systems have been in operation since the mid-70's. This paper will give specific examples of zero liquid discharge operations from 1974 to the present, showing how evaporation equipment and processes have changed to meet the requirements of industry and environmental regulations.

Jan 1, 1996

By Young-Dae Kim, Dong-Sic Kim, Jong-Jin Pak, Kyung-Hyo Do

"Sulfur is one of the most harmful elements in stainless steel (SIS) products and the specification of sulfur content is getting more severe for high grade SIS. In order to accurately control the desulfurization reaction in high chromium containing SIS melts, it is important to know the thermodynamic interaction between chromium and sulfur in Fe-Cr melts over a wide range of chromium content. In this study, the equilibrium sulfur distribution, Ls, between a Ca0-Alz03 slag and Fe-Cr-C,.,-S melts were measured under CO atmosphere in the temperature range of 1823-1923 K. The specific effect of chromium on the activity coefficient of sulfur in the melts was determined with the consideration of carbon effect on sulfur. A separate experiment was carried to determine. Ls between a slag and FeCr- S melts (Cr: 0-30 mass%) at 1873K to check the validity of the thermodynamic parameter determined in the present study.IntroductionFerritic stainless steels containing chromium (Cr) up to 30 mass% have been developed for a good corrosion resistance and a high formability to replace austenitic SIS. Especially, Sulfur (S) causes a reduction of high-temperature strength and the hydrogen induced cracking (HlC) in stainless steel for line pipes. [l]Many studies on the desulfurization of hot metal and liquid steel have been carried out for several decades and they used HzS-H2 gas equilibrium technique for measuring the effects of many alloying elements on the activity coefficient of S in liquid iron. However, the study on desulfurization of Fe-Cr melts was very scarce.[2] In order to accurately control the desulfurization reaction of high Cr stainless steel, it is essential to know the thermodynamic relation between Cr and S in Fe-Cr melt over a wide range of Cr content and temperature.In the present study, the thermodynamic interaction between Cr and S in liquid iron was determined by measuring the equilibrium distribution ratios of S between Fe-Cr-C,.1-S melts containing a wide range of Cr up to 30 mass% and a 55 mass%Ca0-45 mass%Alz03 slag of which the sulfide capacity was pre-determined using Fe-C,a1-S melts in the temperature range of 1823-1923 K. The validity of thermodynamic parameter determined in the present study was checked by measuring the S distribution between a Ca0-Alz03-Mg0 slag of known sulfide capacity and liquid Fe-Cr-S alloy at 1873 K. Using Wagner's formalism, the results of experiment were thermodynamically considered to determine the effect of a specific concentration of Cr on the activity coefficient of S in liquid iron."

Jan 1, 2014

By Lenny Winkel

With the aim to develop a solar-driven process for the extraction of copper from sulfide concentrates research on the decomposition of copper sulfides under inert atmospheres has been initiated. Thermogravimetric measurements on chalcocite,(Cu2S) revealed that copper is formed already at 1823 K. Chalcopyrite (CuFeS2) also disintegrates at this temperature, although at a lower rate. Copper and iron have been identified in the solid residue. The results confirm the feasibility of copper extraction by direct decomposition of sulfides under atmospheric pressure. The decomposition under inert atmosphere prevents generation of SO2, it also alters the behavior of volatile impurities during decomposition of copper sulfide concentrates. Chemical equilibrium calculations for chalcopyrite contaminated with enargite (Cu3AsS4) have shown that the absence of an oxidic slag allows for a complete evaporation of arsenic and subsequent separation from intermediate sulfides. The need to better assess the potential of direct sulfide decomposition has prompted the development of an experimental setup for studying the decomposition reactions. The experiment has been devised such that data on the decomposition kinetics and on impurity removal can be obtained at temperatures up to 2500 K.

Jan 1, 2003

By Nicholas Zabaras, Deep Samanta

"Solidification of metal aluminum and aluminum alloys is modeled on uneven surfaces characterized by sinusoidal curves. Wavelengths and amplitudes of these sinusoidal surfaces are varied to study their effects on processes like solidification, macro-segregation and inverse segregation. Solidification and macro-segregation are modeled using a slightly modified form of a stabilized finite element method developed recently to model high Rayleigh number solidification and porous media flows. For pure metal solidification, the effect of varying amplitudes and wavelengths is observed in heat transfer, fluid-flow ~nd phase change processes. The relative importance of shrinkage driven flow and solutal convection on the redistribution of solute for an alloy solidifying in a rectangular cavity is compared. The analysis is then extended by modifying one of the surfaces to a sinusoid. In this case the effects of varying amplitudes and wavelengths are studied in heat transfer, fluid flow, phase change, macro-segregation and inverse segregation processes.1 IntroductionTransport phenomenon during solidification of alloys is a major cause ofcasting defects such as segregation, micro-voids, hot tears, porosity, internal and surface cracks. Heat flow across metal and mold surfaces directly affects the phase change process and plays an important role in determining freezing conditions within the metal. In alloys, natural convection and shrinkage play an important role in determining the final solute redistribution, macrosegregation and evolution of solid macromorphology. Surface unevenness plays an important role during the early stages of solidification. It influences the heat transfer rate and fluid flow in the melt, which in turn affect the morphology and shape of the solid-liquid interface. The effect of surface unevenness on solute redistribution is important during solidification of alloys, where solute driven flow in the mushy zone is prominent. Thevik and Mo in [7] and [8] used a one dimensional model for studying surface segregation and macrosegregation in alloys under the influence of exudation and solidification shrinkage. Air-gap formation in their model was expressed through a variable convective heat transfer coefficient at the boundary. Tsai et al. in [3] and [4] have modeled macrosegregation in an aluminum-copper alloy driven by shrinkage and solutal convection. They used a single domain model based on mixture theory and solved the transport equations using finite difference methods. Our aim is to model solidification of aluminum followed by macrosegregation and inverse segregation in aluminum-copper alloys on uneven surfaces by finite element methods. These surfaces are modeled as sinusoids characterized by amplitudes, ?s and wavelengths, As, By varying As and ?s, changes in heat transfer, fluid flow, phase-change and macrosegregation are studied."

Jan 1, 2004

By P .. R. Ammann

A two-stage pyrometallurgical process has been developed for the recovery of copper (and other non-ferrous metals) from copper smelter slags. All types of slags, including highly oxidized, converter-type slags, are cleaned in an electric furnace which employs mechanical mixers to promote magnetite reduction and copper extraction at high rates. In a 10-ton pilot furnace, it has been demonstrated that slags can be cleaned to 0.2-0.3 per cent copper with economically acceptable usage of raw materials and energy; copper is recovered as a high-grade matte. Pilot plant data have been scaled up to a commercial furnace and engineering designs have been made for a furnace to treat 60 tons per hour of slag from a Noranda Reactor and the associated converters. Plans are being formulated for the construction of a prototype slag cleaning furnace.

Jan 1, 1976

By Rick Honaker

Rare earth elements (REEs) contained in coal and associated mineral matter exist in several forms including micro-dispersed minerals, ion adsorption onto clay surfaces, and chemically bound. Tests found that REEs can be effectively recovered from certain components of three coal sources by leaching under mild conditions followed by solvent extraction. A range of pH values were evaluated at solution temperatures of 25 and 75 °C. When using 1.2 M of sulfuric acid, nearly 85% recovery of the REEs was extracted from the middlings material collected from an operating plant. Acid leaching of a second middling source from another plant resulted in 60% of the total REEs being recovered under the same leaching conditions. Solvent extraction treatment of the leachate produced from six different coal sources resulted in products containing up to 50% total REEs from feedstocks starting with around 300 ppm.

By Vladimir Panjkovic, Ostrovski. Oieg, Campbell Cripps Clark, John Truelove

"Effects of properties of raw materials and blast on the performance of an iron bath reactor have been examined by a mathematical model. The model consists of three modules: 1) chemical reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, post-combustion ratio and heat-transfer efficiency, temperature and composition of the off-gas, and slag and metal chemistry.IntroductionOne of the anticipated advantages of smelting reduction over conventional ironmaking is the use of lower-grade raw materials. In this work, the effect of-properties of raw materials on the performance of an iron-bath reactor is examined with a numerical model. The model is also used to assess the effect of properties of the blast (flowrate, temperature and oxygen enrichment) and ejected droplets (generation rate, size and ratio of total weights of slag and iron droplets) on the key parameters of the process. In the process coal, oxygen, ore (which may be partly prereduced) and fluxes for specified slag composition are charged to the bath. Slag and iron droplets are ejected from the bath into the gas phase, where they are heated before returning to the bath. Iron droplets undergo decarburisation and reoxidation with CO2 and H2O. Dust is also generated from the bath, and oxygen or preheated air for post combustion is injected from the top of the vessel.The model consists of three modules: 1) reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The structure of the model and the data exchange between the modules are shown in Fig. 1. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, postcombustion ratio (PCR), heat transfer efficiency (HTE), off-gas temperature and composition, slag and metal chemistry, and rates of decarburisation and reoxidation of the iron droplets."

Jan 1, 1996

By Ramana G. Reddy

Thermodynamic modeling and experimental study on impurity capacities and their distribution between mattes or metal and slags in smelting, converting and refining of non-ferrous metals was discussed. A brief review on the recent developments in copper smelting and converting is presented. The analysis showed that, copper smelting capacity increased by a factor of 10 since 60's, smelting rate increased by a factor of more than 5 and process fuel equivalent decreased by a factor of 2. A thermodynamic model for prediction of impurities capacities in slags and their distribution in mattes and slags was developed. The impurities capacities (i.e. sulfur and arsenic) of slags were calculated a priori with no adjustable parameters using the Reddy-Blander model. The capacities predictions were made in a wide range of matte and slag compositions, PSo, and temperatures in conditions pertaining to copper and lead industrial slags. The calculated results for sulfide and arsenate capacities are in good agreement with the available experimental and industrial copper and lead industrial slags data. The sulfide and arsenate capacities in copper slags (fayalite, ferrite and olivine) and lead slags are reviewed. The application of RB model predicted ratios of O2 and S2 partial pressures in industrial copper smelting processes are discussed. Application of this model for the prediction of Sb, Bi and other impurity capacities and their distribution ratios in mattes or metal and slags, in industrial smelting and refining processes is discussed.

Jan 1, 2003

By A. S. Usrnani

Due to both turbulence and the highly variable geometry of castings, a realistic numerical simulation of the metal flow is prohibitvely expensive with current technology. However, when the chief purpose is to achieve realistic thermal fields a precise How simulation is not necessarily required. In this paper we assume a laminar flow regime and obtain the flow field by solving the incompressible Navier-Stokes Equations using a velocity-pressure segregated semi-implicit finite element method. The free metal surface is predicted by advecting a pseudo-concentration function via the computed How field. This involves an explicit finite element solution of a pure advection equation. The thermal field is calculated by solving the convective-diffusive energy equation by an explicit finite element method using the computed flow field and the location of the free surface. All the advection terms are discretized using a Taylor-Galerkin method. The interface between the metal and mould is modelled using special interface elements. The model is demonstrated by solving practical example problems. The results show that a sharp thermal front is maintained during the course of filling without excessive diffusion. The heat diffusion in the mould can be controlled by varying the metal mould heat transfer coefficient.

Jan 1, 1994

By Sevket Acar, Tim Acton

"Zarafshan/Newmont is a 50/25/25 joint venture between Newmont Gold and the State Committee for Geology and Mineral Resources, and Navoi Mining and Metallurgical Combinat, two entities of the Republic of Uzbekistan. The Zarafshan/Newmont joint venture consists of a heap leaching operation which will process 220 million metric tonnes of existing low-grade oxide ore stockpiles (averaging 0.036 oz Au/t) from the Muruntau mine. Net recovery over the 17-year life of the project is expected to be 4.8 million ounces of gold.The plant construction started in October 1993 and operations commenced on May 25, 1995. The crushing plant consists of four stages of crushing and screening to produce a 95% passing 3.35 mm product, followed by heap leaching and gold recovery by the Merrill-Crowe process. The dore metal is refined at the Muruntau refinery. All gold produced by the joint venture is sold on the world market. IntroductionThe Muruntau mine and nearby town of Zarafshan are located in the center of the Kyzylkum desert, 250 miles west of Tashkent, capital of Uzbekistan. Following a mining conference in Moscow in 1990, a Newmont geologist was among the first team of westerners to visit the Muruntau Mine, the second largest gold producer in the former Soviet Union. At Muruntau, they found 220 million tonnes of low grade gold ore that had been stockpiled during the previous 25 years. In February, 1992, six months after Uzbekistan's independence, Newmont signed a 50/50 joint venture agreement with the Uzbek government to use heap leach technology to process the ore. The feasibility study was completed in November of 1992. Plant construction started in October, 1993 and operations commenced on May 25, 1995.Newmont Metallurgical Services performed metallurgical studies to obtain heap leach process design criteria parameters. The initial metallurgical study on 20 grab samples is the subject of this paper."

Jan 1, 1997

By James M. Fragomeni

"The mechanical behavior of an Al-Li alloy was studied and related to the extrusion processing parameters, the plastic metal flow during defonnation, the anisotropy, and the microstructure. The extrusion temperatures, strain rates, extrusion ratios, billet temperatures, and extrusion geometries were varied during processing and correlated with the microstructure and properties. The extrusion processing variables were related to the mechariicar behavior, anisotropy, and microstructure through the ZenerHollomon parameter i.e., the temperature compensated strain rate. Based on optical and electron microscopy studies it was found that regardless of the extrusion conditions, the various microstructures for the most part were unrecrystallized for both the as-extruded and the solution heat-treated conditions. Smaller grain sizes were correlated to larger Zener-Hollomon parameters. The extrusion temperature and ratio did not significantly affect the strength or ductility as did the section geometry, which had a large affect on these mechanical properties. The anisotropy of the properties varied substantially when comparing the extruded longitudinal versus transverse grain orientations.IntroductionThe extrusion process also has a substantial influence on: the microsfructure and mechanical properties of a material that is Athens, Ohio, 45701 fonned The plastic defonnation that occurs during the extrusion process alters the grain size, crystallographic texture, anisotropy, subgrain size, dislocation density and various other microstructural features. Often the material being extruded is not homogeneous, therefore variations in the microstructure and properties occur across the cross-section of the final extruded product. The mechanical properties and microstructure can also vary with length since it is hard to maintain a constant temperature throughout the extrusion process. The extrusion temperature often varies from the heat generated during the extrusion process. The demonstration material that was extruded for this .study was an aluminum alloy containing 2.6wt, % lithium and 0.09wt.% zirconium. This alloy was strengthened by heat treatment causing nucleation, growth, and coarsening of coherent metastable o' (Al3Li) precipitates in the microstructure. The ? precipitates which are a consequence 9f artificially aging the AlLi alloy, are spherical, ordered, and coherent with the aluminum matrix and impede the dislocation glide inotion during plastic defonnation. Theo particles grow homogeneously in the matrix, and have the Cu3Au (L 12)"" superlattice crystal structure. Aluminum-lithium alloys are used primarily for aerospace structural applications since they have attractive properties such as a lower density and higher elastic modulus than conventional 2XXX and 7XXX alloys."

Jan 1, 2000

By H. Yin, T. Emi

"Advantages of gas/flux injection technology as materialized in the main stay unit processes for steelmaking are depicted covering hot metal pretreatment through secondary refining. Current status of micro-kinetic issues involved in the injection technology are reviewed including gas-in- metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly addressed to further develop injection technology for steelmaking processes.1. FROM PAST TO PRESENTApplication of gas injection to steel industry started in early 1950's when inert gas bubbling via stopper rod, lance, or porous refractory plug was practiced to make the temperature of steel melt in ladle uniform The gas bubbling in ladle was then extended to slightly removing hydrogen ti'om the steel melt tapped from Electric Arc Furnace (EAF) and Basic Open Hearth Furnace (BOH) when vacuum processing facilities were not popular. Later, oxygen gas injection via calorized steel pipe into molten steel bath in BOH Furnace was also put into operation to promote the decarburization to increase the productivity of the process. This line of development has been made in parallel with more profound processes, i.e, top blowing Basic Oxygen Furnace (BOF) for primary steelmaking and side blowing Argon Oxygen Oecarburization (AOD) vessel for decarburizing stainless steels.On the other hand, injection of fluxes into steel bath was first industrialized in Germany in 1960's, Primary objective was to desulfurize steel melt in ladle by injecting CaC2 or CaCrCaO mixture via lance under neutral slag cover with good success. Difficulties in injecting fluxes without clogging and rippling at a desired flux/gas ratio, and durability of injection lance were resolved in due time to bring forth many injection facilities to flourish for versatile refining operation. Top injection of fluxes from main oxygen lance to BOF was also industrialized as LDAC to promote early slag formation. A new process then emerged which injects oxygen gas and fluxes together through concentric annular tuyere, installed at the bottom of the BOE into steel melt. This process, developed in Germany [Oxygen Bottom Maxhutte (OBM)] and brought into maturity in USA (Q-BOP) and Japan in a large scale operation, became the predecessor of the combined blowing (top and bottom blown) BOF which dominates modern steelmaking."

Jan 1, 1996